WASHINGTON — The chairman of the House Intelligence Committee said Tuesday that lawmakers are worried about the possibility of further disclosures about the government's sweeping electronic surveillance and the impact that could have on efforts to combat terrorism.

"We don't want to make this thing more damaging that it already has become," Rep. Mike Rogers, R-Mich., said ahead of an open hearing the Intelligence Committee scheduled with Army Gen. Keith Alexander, head of the National Security Agency. Rogers said lawmakers, however, "know there are dozens" of terrorist plots that have been foiled by the programs.

Rogers said he expects the government to declassify additional information about the wide-ranging telephone surveillance program and a companion Prism program targeting the Internet and e-mail communications.

On the basis of information the administration had declassified earlier in the wake of revelations about the program by former NSA contract employee Edward Snowden, members of Congress feel certain that the eavesdropping should be credited for thwarting an attempted attack on New York City's subway system, said Rogers in an appearance on NBC's Today show.